After OpenOffice / LibreOffice restart, you should see new bar. Note, in order for the plugin to work, Mendeley has to be running.

What’s great about this plugin, you can adjust citation style by just a few clicks by clicking on `Choose Citation Style`. There is quite extensive database of predefined citation styles, so adjusting the reference style to your favourite journal will take just a few seconds 🙂
More info about the plugin on github.